1. Field of the Invention
This invention generally relates to ball grid array (BGA) integrated circuits and more specifically to trays for the storage and transport of such BGA integrated circuits.
2. Description of Related Art
The storage and transportation of semiconductor components, such as BGA integrated circuits are important considerations in the production of electronic assemblies. Trays for the transport and storage of individual types of integrated circuits have emerged as important complementary products. Such trays have become popular because each tray can carry a plurality of integrated circuits and each tray can be stacked with other trays. A set of stack trays constitute an efficient means for shipping large numbers of individual integrated circuits. As these trays have grown in popularity, certain functional requirements have been defined. For example, trays must provide a direct, repeatable position correlation between the tray and the terminals on the integrated circuit. Trays must protect terminals from damage due to mechanical shock during transport. They must also prevent damage due to the accumulation of electrostatic charges.
Historically the semiconductor industry has developed a number of different integrated circuit packages. These packages have included, among others, TSOP, QFP, and PGA packages. Trays have been designed for those specific packages. The same development has occurred with respect to BGA integrated circuits, and there are a number of commercially available trays for such devices. For example, U.S. Pat. No. 5,400,904, assigned to the same assignee as this invention, discloses one such BGA tray. An outer frame defines discrete storage pocket areas. Inwardly facing tab surfaces extending from the framework in each pocket area define a first support plane for engaging the component in a first, or terminals down, orientation by engaging the periphery of the BGA integrated circuit adjacent an outer band of terminals. Second inwardly facing tab surfaces in each storage pocket area engage the other side of the BGA integrated circuit to support it in a terminals up position when the tray is inverted to a second orientation. Opposite offset wall portions on each side of the tray stabilize the component in the housing plane in either orientation. The offset allows these opposite extending wall portions to interfit when trays are stacked.
U.S. Pat. No. 5,551,572 (1996) to Nemoto discloses another version of a BGA tray. In this tray the structure that supports the BGA integrated circuit component in a terminals down position includes a peripheral edge formed in the storage pocket area. The edges are formed to partially surround the peripheral solder terminals thereby to increase the supporting surface for the BGA integrated circuit component.
When trays according to the foregoing patents were developed, the terminals were spaced from the edge of the integrated circuit. This defined a predetermined peripheral area for support. Now, however, as BGA integrated circuit manufacturers seek to increase the density of integrated circuit terminals in part, they are minimizing the free surface about the periphery of the device. It has become difficult to adapt the existing tray structures for these densely populated integrated circuits to provide a reliable support for BGA integrated circuits without damaging the outer terminal balls.